1. Field of the Invention
The present invention provides an illumination system, and more particularly, to an illumination system which is for use in a projection device, has less optical components and can improve the light combining efficiency.
2. Descriptions of the Related Art
Because solid light sources such as lasers and light emitting diodes (LEDs) have advantages, such as saving energy, a high light-emitting efficiency, a concentrated luminance and a long service life, the use of the solid light sources as light sources of projection devices has received much attention in the art. In U.S. Patent Publication No. US 2009/0262308, a light source unit and a projector 10 are disclosed. As shown in FIG. 1, the light source unit 63 has a red LED 161R, a green LED 161G and a blue LED 161B, and light beams are combined through a plurality of condensing lenses 164 disposed adjacent to the LEDs 161R, 161B and 161G respectively. It shall be noted that the light source unit 63 has to condense the light beams through the condensing lenses 164 disposed adjacent to the LEDs 161R, 161B and 161G to combine the light beams; therefore, in this U.S. Patent Publication, the light source unit 63 has to be provided with a large number of optical components, which increases the weight of the light source unit 63. Moreover, sufficient space is needed in the projector 10 to accommodate the light source unit 63. Consequently, this type of light source unit is limited by the volume and is unsuitable for use in a miniaturized projector.
In view of this, an urgent need exists in the art to provide a solution that can effectively arrange a plurality of light sources and optical components in a projector so that the light-emitting efficiency is improved while the volume and the weight of the light emitting source can still be effectively reduced.